Speaker
Description
The search for a solution to the tensions in the Standard Model in the shape
of a single, all-describing model is both extremely needed and extremely hard to
carry out. This is partly because we lack the knowledge of some of the fundamental
aspects that a new theory should include in order to match our observations of the
universe. Even in the case of the ΛCDM model itself, which we take as our most
general description of the universe at large scales, it is not clear what components
such as Λ and CDM (!) are supposed to be consisting of.
As an alternative, we can consider phenomenological extensions or modifications to
the standard theory, which aim at detecting a deviation from the standard framework
rather than explaining their fundamental nature.
I will be presenting the results of an analysis carried on the growth index - ’γ L ’, a
highly precise parametrisation that modifies the growth of linear, sub-horizon matter
perturbations in the Standard Model, but not its expansion history. Through the
lens of a variety of CMB datasets, we have studied how the ad-hoc inclusion of
the fixed parameter γ L behaves when confronted with the problematic H 0 and S 8
tensions, while also searching for the presence of deviations from its ΛCDM value:
γ L ≈ 0.55.
